David Wootton is shocked and intrigued by a strange play about sex: Caryl Churchill's Cloud Nine at the Almeida Theatre

It's now four days since I saw this play, and I'm still a bit shellshocked. In fact, the truth is I'm plain shocked. But then Caryl Churchill (who is perhaps best known for Top Girls) loves to shock, and this play, first performed in 1979, still packs a punch. A simple indicator of the world we are in is the cast list of the text (published by Nick Hern Books):

Except for Cathy, characters in Act II are played by actors of their own sex.

In Act I, by contrast, we have a man playing a wife, a woman playing a boy, and a white playing a black. Even in Act II, a four year old girl (Cathy) is played by a man with a moustache. Act I is set in the colonies under Queen Victoria; Act II is set in England in 1979, defined as twenty-five years later. There are seven actors in Act I and the same seven in Act II; two of the characters from Act I reappear in Act II, but played by different actors. I trust that's clear.

One thing one can say with absolute certainty: the acting is wonderful. It seems invidious to single out any individual when all are superb - and superb in a tiny theatre where there is absolutely no place to hide, where the slightest break in concentration is immediately visible. Still, where inevitably most of the actors are rather obviously acting most of the time, in Act II Sophie Stanton disappears into the part of Lin, a lesbian mother. This is acting so fine as to become invisible. Mark Letheren (Wire in the Blood) and Nicola Walker (Spooks) are at least as good as the others. Nicola Walker's monologue on rediscovering the joys of masturbation quite takes the breath away.

So we're all agreed. In Act I everybody is at it, but nobody (or almost nobody) is supposed to be. There's adultery, homosexuality, lesbianism, paedophilia, and married love - but not very much married love. In Act II there's adultery, homosexuality, lesbianism, married love (again in rather short supply) - and incest. The truth is that it is the incest (sibling incest, and of a rather innocent sort) that shocked me.

Churchill has, I think, a theory about sex. It goes roughly like this. Everybody is keen on it. Some people like it in one particular way, and know what they want; others aren't quite clear what suits them best, and so don't know what they want. All in all, she seems to think, sex is pretty harmless; unlike fear, anger, repression, and monogamy, which are always to be deplored. The notion that society requires some sort of repression of the sex drive for its own survival appears to be incomprehensible to her. In that respect, if in no other, her view is a rather innocent one.

The play is a test of the actors, deliberately, and of the audience, equally deliberately. Its structure is somewhat perverse - it is hard to forget that there are more than twenty-five years between 1901 and 1979. It would be very easy to get very impatient with it, and I was a bit impatient with Act I, where everyone is a stereotype. But the cardboard cut-outs of Act I are replaced in Act II by real people (even Cathy, if you can believe it). They change, they develop, they grow in front of our eyes. As Churchill herself says,

all the characters in this act change a little for the better.

In particular Betty, the eldest character on the stage, leaves her husband, rediscovers her children, and tries to rediscover sex - Nicola Walker does this wonderfully, but it is a complex part to play. The play ends with a strange sense of hope in the midst of human imperfection. It is not a great play, but it is a good one. And it is already an intriguing period piece: who would imagine, as we watch the events of 1979, that Thatcher is just around the corner (the first night of Cloud Nine was Valentine's Day, and Thatcher was elected on 4th May). Above all, you won't see better acting anywhere - and the playwright and the director deserve their full share of the credit.